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Feb. 11, 2009 -- The number of Americans suffering from chronic low back pain is on the rise, and a new study says the nation’s obesity epidemic may be partly to blame.

In North Carolina, the percentage of people suffering from chronic low back pain has more than doubled since the early 1990s, according to researchers, who see the state as a mirror of the nation.

“Low back pain is the second most common cause of disability in the United States and a common reason for lost work days,” Janet Freburger, PhD, PT, of the University of North Carolina, and colleagues write.

Individuals in the study were considered to have chronic low back pain if they reported pain and activity limitations nearly every day for the three-month period prior to their interviews, or if they reported more than 24 episodes of pain that limited their activity for one or more days in the prior year.

The team of researchers found that the prevalence of chronic low back pain in North Carolina increased from 3.9% in 1992 to 10.2% in 2006.

Increases were noted in men and women, and also across all ages and racial and ethnic groups.

The results were gathered in telephone surveys of 4,437 North Carolina households in 1992 and 5,357 in 2006. Questions were aimed at determining prevalence of low back pain or neck pain sufficient to limit daily activities.

The study, published in the Feb. 9 issue of the Archives of Internal Medicine, is thought to be the first to use similar methods and a consistent definition of chronic low back pain to analyze trends over time.

More than 80% of Americans will experience an episode of low back pain at some time in their lives, and total costs of the condition are expected to exceed $100 billion annually, two-thirds of that from decreased wages and productivity.

The researchers say reasons for increased prevalence aren’t clear but could be linked to rising obesity rates and depression, as well as heightened awareness of symptoms.

The changing nature of the nation’s workforce, with an increase in construction and service industry jobs and a decline in manufacturing, may be another factor.

“Discerning whether the prevalence of this condition is increasing and contributing to the increase in the use of health care services is vital for developing strategies to contain costs and improve care,” Freburger says.